GATING PROCESSES OF CHANNELS INDUCED BY COLICIN-A, ITS C-TERMINAL FRAGMENT AND COLICIN-E1 IN PLANAR LIPID BILAYERS
GATING PROCESSES OF CHANNELS INDUCED BY COLICIN-A, ITS C-TERMINAL FRAGMENT AND COLICIN-E1 IN PLANAR LIPID BILAYERS
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DOI：
10.1007/bf00253839
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发表时间：
1987-01-01
影响因子：
2
通讯作者：
PATTUS, F
中科院分区：
文献类型：
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作者：
COLLARINI, M;AMBLARD, G;PATTUS, F
大肠杆菌素A及其C-末端20 kDa片段形成的孔的pH和膜电位的依赖性已被测量使用平面脂质双层。由大肠杆菌素A和片段形成的孔的单通道电导随pH增加，表观pK为6.0。在pH 5.0时，由大肠杆菌素A或其片段形成的通道的膜电位门控是相同的。在相同的pH值下，当使用相关的细菌素大肠杆菌素E1时，发现非常相似的孔特性。与以前的研究一致，这些数据表明，含有孔腔的蛋白质结构位于大肠杆菌素A的20 kDa C-末端部分，并有利于最近提出的模型，基于蛋白质序列分析，提出大肠杆菌素A，E1和IBC-末端结构域折叠在相同的三维结构。然而，它也表明，大肠杆菌素A，而不是它的C-末端片段经历了一个pH依赖性的过渡之间的“酸性”和“碱性”形式的孔与表观pK为5.3。这两种形式的孔的不同之处在于它们的门控电荷，而不是通道尺寸。这些结果表明，有一个pH依赖性的关联之间的C-末端结构域携带的孔腔和另一个域的分子，影响孔膜电位的敏感性。
The dependence on pH and membrane potential of the pore formed by colicin A and its C-terminal 20 kDa fragment has been measured using planar lipid bilayers. The single channel conductance of the pore formed by both colicin A and the fragment increases with pH with an apparent pK of 6.0. At pH 5.0 the gating by membrane potential of the channels formed by either colicin A or its fragment is identical. At the same pH, quite similar pore properties were found when using the related bacteriocin, colicin E1. In agreement with previous studies, these data indicate that the protein structure containing the lumen of the pore resides in the 20 kDa C-terminal part of the colicin A and favours the recently proposed model, based on protein sequence analysis, which proposes that colicin A, E1and IBC-terminal domains are folded in the same three-dimensional structure. However, it is also shown that colicin A and not its C-terminal fragment undergoes a pH dependent transition between an “acidic” and a “basic” form of the pore with an apparent pK of 5.3. The two forms of the pore differ by their gating charge but not by the channel size. These results suggest that there is a pH dependent association between the C-terminal domain carrying the lumen of the pore and another domain of the molecule which affect the pore sensitivity to membrane potential.